The most essential parts of a stair lift that you should be aware of are as follows; power, controls, chair, drive and of course the track itself.
The power that runs the lift varies; battery powered tracks are the most common with a 24v these are handy because you don’t have to have a new outlet installed. The other methods are cords that move along with the chair/motor assembly. One type has batteries but is constantly charged. The other type relies solely on the AC power. The downfall to either of these is the tethered cable. It is constantly winding and unwinding and can eventually fail causing problems and requiring repair service.
Next are the controls you will need controls to move the lift from point A to point B. There are two options; a handheld device or a wireless device generally running on batteries. As for the chair you will need to make sure it supports the weight you are planning on putting on it.
Another good buy is to make sure your chair swivels either 90 or 180 degrees, this helps with the person getting on and off of the lift, also consider a footrest.
The drive transfers the movement of the chair and operates the lifting and lowering, the most common drive is a rack and pinion. The older technology is a cable system that has screws and drives. The track design varies on whether or not you have and curves in your stairs, the least expensive tracks are a straight shot. When purchasing your lift consider all the parts involved and the maintenance it will take to keep it up and running.